DESCRIPTION (Verbatim from the Applicant's Abstract): The proposed research uses a disarmed Herpes viral vector carrying the marker gene for Green Fluorescent Protein (GFP) to mediate antisense knockdown of the K-Ca channel, rslo, of rat cerebellar Purkinje neurons. Preliminary data show that antisense knockdown of rslo causes a measurable decrease in the abundance of K-Ca channels in Purkinje neurons, and that viral-driven antisense against another K+ channel beta subunit (Kvbeta1.1) dramatically affects whole cell firing patterns, thus demonstrating the feasibility of the viral vector antisense approach. Expression of the alpha subunit of the K-Ca channel rslo is regulated in cerebellum by depolarization and Ca2+ entry in a temporal pattern that is comparable in vivo and in vitro. Electrophysiology, molecular biology, immunocytochemistry and fluorescence imaging are used to analyze the consequences of viral infection, molecular antisense manipulations, and to evaluate the role of the K-Ca channel in the generation of the classic pacemaker firing pattern of Purkinje neurons. Aim 1 uses viral-driven antisense against the alpha sequence to analyze the function of K-Ca conductance in generating pacemaker firing. Aim 2 analyzes the expression of the rslo beta subunit in cerebellum, and uses viral-mediated overexpression and underexpression to dissect the contribution of the beta subunit to the maturation of the pacemaker firing pattern. The disarmed viral vector is a powerful new approach for manipulating gene expression in neurons in vivo and in vitro. A number of human neurological developmental disorders affect the cerebellum; its extended postnatal developmental period constitutes a window of vulnerability to clinical agents with neurological side effects. The rat provides a useful model for studying postnatal cerebellar development and neuropathological damage, and may provide insights into methods to manipulate developmental abnormalities in the cerebellum.